Depression-like symptoms found in smokers trying to quit: Study

The findings were based on brain scans of 48 subjects, half of whom were non-smokers and the smoking factions were evenly divided between those who smoke 15 to 24 cigarettes a day and those who smoke 25 or more.

Photograph by: Natasha Fillion
, The Gazette

A new study shows another possibility for why people struggle to quit a habit that kills millions of people around the world each year and tens of thousands in Canada.

The Toronto-based Centre for Addiction and Mental Health released a study Tuesday that showed people who smoke a pack or more of cigarettes daily had elevated levels of a protein known as monoamine oxidase in their brains in the early stages of abstaining from smoking.

The same chemical is known to be at high levels in people suffering from clinical depression.

The elevated levels of monoamine oxidase were discovered in this study with brain scans among heavy smokers eight hours after having their last cigarette. These smokers also reported increased feelings of sadness in questionnaires done as part of the study.

Monoamine oxidase is a protein that feeds on other chemicals in the brain, such as serotonin, that helps regulate mood. While past research has shown elevated levels of monoamine oxidase in people diagnosed with clinical depression, creators of this study said it was the first time it was studied in relation to cigarette withdrawal.

The researchers said such findings could explain why smokers are at a higher risk of suffering from depression — almost twice that of the general population, according to Jeffrey Meyer, a senior scientist with the Centre for Addiction who led the study.

The findings were based on brain scans of 48 subjects, half of whom were non-smokers and the smoking factions were evenly divided between those who smoke 15 to 24 cigarettes a day and those who smoke 25 or more.

Those in the heavy-smoking category saw their monoamine oxidase levels rise about 25 per cent eight hours after having their last cigarette. No significant change was seen among the more moderate smokers.

It also provides another possible reason why quitting smoking is so difficult — creating unpleasant emotions among those attempting to stop— with Meyer saying the effect uncovered in this study is completely separate from nicotine addiction.

The study said a key factor in the findings could be the presence of a substance called harman in cigarette smoke. This suppresses monoamine oxidase in the brain of a person who has just had cigarette. The study shows that this substance rebounds to higher-than normal levels in heavy smokers in withdrawal.

"There's a lot of different chemicals in cigarettes," Meyer said in an interview, adding that identifying other potentially addictive qualities in tobacco could help improve people's chances of quitting smoking.

"The more we understand about mechanisms, the more sophisticated prevention strategies we can come up with. There's been a lot of focus on nicotine — and there should be — but here's another area that we could focus on to help people."

For example, he suggested efforts could be made to develop drugs that suppress monoamine oxidase in people who are trying to stop smoking.

Harman is what tryptophan — a chemical in cigarettes — turns into when burnt.

Some of the other suggestions that arose from this study included designing cigarette filters that more effectively screen out harman and reducing the amount of tryptophan in cigarettes.

Meyer said harman is also found in certain alcoholic beverages, such as beer and wine. He is involved in ongoing research exploring possible links between harman and alcohol addiction.

No immediate reaction to this study was available from major producers of cigarettes in Canada, such as Imperial Tobacco, Rothman, Benson & Hedges, and JTI-Macdonald.

Health Canada says 37,000 die annually in Canada each year from smoking, mostly from ailments such as lung cancer and heart disease. The World Health Organization puts the global death count from tobacco use at five million a year.

Story Tools

The findings were based on brain scans of 48 subjects, half of whom were non-smokers and the smoking factions were evenly divided between those who smoke 15 to 24 cigarettes a day and those who smoke 25 or more.

We encourage all readers to share their views on our articles and blog posts. We are committed to maintaining a lively but civil forum for discussion, so we ask you to avoid personal attacks, and please keep your comments relevant and respectful. If you encounter a comment that is abusive, click the "X" in the upper right corner of the comment box to report spam or abuse. We are using Facebook commenting. Visit our FAQ page for more information.

Almost Done!

Postmedia wants to improve your reading experience as well as share the best deals and promotions from our advertisers with you. The information below will be used to optimize the content and make ads across the network more relevant to you. You can always change the information you share with us by editing your profile.

By clicking "Create Account", I hearby grant permission to Postmedia to use my account information to create my account.

I also accept and agree to be bound by Postmedia's Terms and Conditions with respect to my use of the Site and I have read and understand Postmedia's Privacy Statement. I consent to the collection, use, maintenance, and disclosure of my information in accordance with the Postmedia's Privacy Policy.

Postmedia wants to improve your reading experience as well as share the best deals and promotions from our advertisers with you. The information below will be used to optimize the content and make ads across the network more relevant to you. You can always change the information you share with us by editing your profile.

By clicking "Create Account", I hearby grant permission to Postmedia to use my account information to create my account.

I also accept and agree to be bound by Postmedia's Terms and Conditions with respect to my use of the Site and I have read and understand Postmedia's Privacy Statement. I consent to the collection, use, maintenance, and disclosure of my information in accordance with the Postmedia's Privacy Policy.